dt-bindings: soc: qcom: Add label for GLINK bindings

There are GLINK clients who open the same channel on multiple GLINK
links. These clients need a way to distinguish which remoteproc they
are communicating to. Add a label property to identify the edge this
node represents.
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NChris Lew <clew@codeaurora.org>
Signed-off-by: NArun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>

Documentation/devicetree/bindings/soc/qcom/qcom,glink.txt

@@ -10,6 +10,11 @@ edge.
 	Value type: <stringlist>
 	Definition: must be "qcom,glink-rpm"
 
+- label:
+	Usage: optional
+	Value type: <string>
+	Definition: should specify the subsystem name this edge corresponds to.
+
 - interrupts:
 	Usage: required
 	Value type: <prop-encoded-array>